Communicating scheduling requests in a wireless network

ABSTRACT

In a wireless communication system including a wireless transmit/receive unit (WTRU) and a Node-B, an uplink (UL) scheduling request is transmitted by the WTRU to the Node-B when the WTRU has buffered (user) data to transmit to the Node-B, but needs to have a scheduling grant for UL data transmission. The WTRU determines whether to transmit to the Node-B a short buffer status information message or a full buffer status information message, based on conditions, whereby the buffer status messages are transmitted with either a short-version UL scheduling request or a full-version UL scheduling request.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/811,560 filed Mar. 6, 2020, which is a continuation of U.S. patentapplication Ser. No. 15/703,424 filed Sep. 13, 2017, now U.S. Pat. No.10,588,046, issued on Mar. 10, 2020, which is a continuation of U.S.patent application Ser. No. 13/932,818 filed Jul. 1, 2013, now U.S. Pat.No. 9,794,824, issued on Oct. 17, 2017, is a continuation of U.S. patentapplication Ser. No. 11/677,091, filed Feb. 21, 2007, now U.S. Pat. No.8,477,695, issued on Jul. 2, 2013, and claims the benefit of U.S.provisional application 60/776,345 filed on Feb. 24, 2006, which areincorporated by reference as if fully set forth.

FIELD OF INVENTION

The present invention is related to wireless communication systems. Moreparticularly, the present invention is related to an uplink (UL)scheduling request (SR) selection mechanism for Internet Protocol(IP)-based wireless communication systems, such as an evolved universalterrestrial radio access (E-UTRA) system.

BACKGROUND

In order to keep the technology competitive for ten years and beyond,both Third Generation Partnership Project (3GPP) and 3GPP2 areconsidering long term evolution (LTE), in which evolution of radiointerface and network architecture are necessary.

In wideband code division multiple access (WCDMA) high speed uplinkpacket access (HSUPA), (Release 6), dedicated control channel, (orprescheduled grant for control), is used. Due to the IP-based nature ofE-UTRA, no dedicated control channel may be maintained for the uplink.The scheduling request mechanism needs to be designed properly tominimize scheduling overhead without much degradation of theperformance, (such as delay).

SUMMARY

The present invention is related to a wireless communication systemincluding a wireless transmit/receive unit (WTRU) and a Node-B. Anuplink scheduling request is transmitted by the WTRU to the Node-B whenthe WTRU has buffered (user) data to transmit to the Node-B, but needsto have a scheduling grant for uplink data transmission. The WTRUdetermines whether to transmit to the Node-B a short-version uplinkscheduling request or a full-version uplink scheduling request, wherebythe short-version uplink scheduling request uses less channel resourcesthan the full-version uplink scheduling request by omitting informationpertaining to WTRU status parameters. The wireless communication systemmay be an IP-based wireless communication system, such as an E-UTRAsystem. The short-version uplink scheduling request is a one-bitindicator or a multi-bit indicator that indicates an amount ofscheduling grants or resources requested. The full-version uplinkscheduling request includes at least one of a WTRU buffer status and aWTRU link budget.

If the WTRU's current scheduling grant is not sufficient to complete thecurrent transmission of buffered data by a predefined delay, and if asufficient scheduling grant will be provided after the WTRU transmits apredetermined number of short-version uplink scheduling requests to theNode-B, the WTRU may transmit a short-version uplink scheduling requestto the Node-B as in-band signaling.

If the WTRU's current scheduling grant is not sufficient to complete thecurrent transmission of buffered data by a predefined delay, and if asufficient scheduling grant will not be provided after sending apredetermined number of short-version uplink scheduling requests to theNode-B, the WTRU may transmit a full-version uplink scheduling requestto the Node-B as in-band signaling.

The predetermined number of short-version uplink scheduling requests maybe equal to one.

The WTRU may transmit the full-version uplink scheduling request to theNode-B when at least a predetermined number of sub-frames elapsed sincethe last time a full-version uplink scheduling request was transmittedand the WTRU has a scheduling grant.

The WTRU may transmit the short-version uplink scheduling request to theNode-B as layer 1 (L1)/layer 2 (L2) control signaling or higher layersignaling over a contention-based uplink channel if the WTRU iscurrently in an initial power up mode.

The WTRU may transmit the short-version uplink scheduling request to theNode-B as L1/L2 control signaling or higher layer signaling over acontention-based uplink channel if the WTRU has been inactive for apredetermined period of time so that the WTRU is not time synchronizedwith the Node-B in the uplink.

The WTRU may transmit the short-version uplink scheduling request to theNode-B as L1/L2 control signaling or higher layer signaling over acontention-based uplink channel or a low-rate dedicated channel, (i.e.,scheduled channel), if the WTRU is lacking a scheduling grant but stillremains time synchronized with the Node-B in the uplink.

The WTRU may transmit a short-version uplink scheduling request to theNode-B when the WTRU's uplink scheduling request is to be attached touplink acknowledgement (ACK)/negative acknowledgement (NACK) bits,channel quality indicator (CQI) bits, or both, that are transmitted in acurrent transmission timing interval (TTI)/sub-frame.

The WTRU may transmit the short-version, (or full-version), uplinkscheduling request to the Node-B as L1/L2 control signaling or higherlayer signaling over an uplink shared control channel.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description of a preferred embodiment, given by way of exampleand to be understood in conjunction with the accompanying drawingswherein:

FIG. 1 is a flow diagram of an exemplary uplink scheduling requestprocess in accordance with the present invention; and

FIG. 2 is a block diagram of a wireless communication system in whichthe uplink scheduling request process of FIG. 1 is implemented.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “Node-B” includes but is notlimited to a base station, a site controller, an access point (AP), orany other type of interfacing device capable of operating in a wirelessenvironment.

The present invention efficiently combines the usage of theshort-version and full-version scheduling requests for the uplink ofE-UTRA. A short-version uplink scheduling request includes a very smallamount of information to indicate to the Node-B that either of thefollowing events occurs: (1) that the WTRU has data to transmit, but theWTRU has no uplink scheduling grant, or (2) that the current schedulinggrant for the WTRU is not sufficient to complete the transmission of thedata in the WTRU buffer by a predefined delay.

A short-version uplink scheduling request may simply be a one-bitindicator, or it may contain several bits to better indicate the amountof extra scheduling grants or resources requested.

Upon receiving the short-version uplink scheduling request, the Node-Bpreferably allocates or increases a scheduling grant or resources forthe WTRU if there are available resources. If the WTRU has no currentscheduling grant, a predetermined amount of scheduling grant isallocated to the WTRU based on system parameters, including but notlimited to the cell load. If the WTRU has a current scheduling grant,the Node-B increases the scheduling grant by a predetermined amount or apredetermined ratio. The predetermined amount or ratio preferablydepends on system parameters, including but not limited to the cellload.

A full-version uplink scheduling request includes detailed informationabout the WTRU status. The information may include, but is not limitedto, a WTRU buffer status, (e.g., amount of data and prioritiesinformation) and/or WTRU link budget information, (e.g., WTRU powerheadroom).

Upon receiving the full-version uplink scheduling request, the Node-Bobtains comprehensive information about WTRU status. If there areresources available, the Node-B allocates or increases an appropriateamount of scheduling grant or resources for the WTRU to accommodate thequality of service (QoS) requirements of the WTRU, (e.g., delay), giventhe current status of the WTRU, such as the amount of data in thebuffer, associated priorities, and link budget.

When WTRU has data to transmit, the WTRU determines whether to send ascheduling request to the Node-B, (e.g., when there is buffered dataavailable for uplink transmission to the Node-B). If so, the WTRUdetermines whether to transmit to the Node-B a short-version uplinkscheduling request or a full-version uplink scheduling request.

In accordance with the present invention, there are various scenarioswhereby a short-version uplink scheduling request is preferablytransmitted by the WTRU, including but not limited to the followingscenarios.

A first scenario for when a short-version uplink scheduling request ispreferred is when the WTRU just powers up or has been inactive for aperiod of time. That is, the WTRU has no uplink scheduling grant and nocurrent uplink shared channel. In this case, the scheduling request istransmitted as L1/L2 control signaling or higher layer signaling over acontention-based uplink channel. The short-version uplink schedulingrequest, being of small size, is compatible with the very limited amountof control information capable of being transmitted over acontention-based channel, such as a non-synchronized or synchronizedrandom access channel (RACH).

A second scenario for when a short-version uplink scheduling request ispreferred is when the WTRU's scheduling request is attached to uplinkACK/NACK bits, CQI bits, or both, that are transmitted on an uplinkshared control channel in the current TTI/sub-frame. In this scenario,where it has been established that the scheduling request is transmittedin such a manner, the WTRU is aware that the CQI channel or the ACK/NACKchannel is to be transmitted in the current sub-frame or TTI. The WTRUis also aware that there is an uplink shared control channel availablefor its transmission in the current TTI/sub-frame. In this case, thescheduling request is transmitted as L1/L2 control signaling over uplinkshared control channel. Here, the short-version uplink schedulingrequest is compatible with the reasonably small amount of controlinformation that is attached to uplink ACK/NACK and/or CQI since thesefields need to be reserved or configured in advance. Otherwise, when afull-version uplink scheduling request is transmitted, the amount ofwasted resources will be significant when the full-version uplinkscheduling request is not attached to an uplink ACK/NACK and/or CQI.

A third scenario for when a short-version uplink scheduling request ispreferred is when the WTRU's current scheduling grant is not enough tocomplete the transmission of the data in the WTRU buffer by a predefineddelay, and the WTRU expects that a sufficient scheduling grant will beprovided, (if the resources are available), responsive to Kshort-version uplink scheduling requests, where K is preferably a smallnumber, (e.g., K=1). This depends on the scheduling algorithm in theNode-B. In this scenario, a predefined delay is associated with arequired QoS delay requirement of a particular service. For example, ifit is a voice service, a typical predefined delay is around 20-40 msec.As another example, a best effort service such as web-browsing may havea predefined delay in the range of several hundreds of milliseconds toseveral seconds. The delay is measured from the time data is received atthe WTRU buffer from higher layers. In this scenario, the short-versionuplink scheduling request is transmitted as in-band control signaling.

In accordance with the present invention, there are various scenariosfor which a full-version uplink scheduling request is preferablytransmitted by the WTRU, including but not limited to the followingscenarios.

A first scenario for when a full-version uplink scheduling request ispreferred is when the WTRU's current scheduling grant is not enough tocomplete the transmission of buffered data by a predefined delay, andthe WTRU expects that a sufficient scheduling grant will not beprovided, (even if the resources are available), after sending a smallpredetermined number, say k, of short-version uplink schedulingrequests. For example, the value of K may be one. This depends on thescheduling algorithm in the Node-B. In order to reduce the delay toobtain sufficient uplink scheduling grant, the WTRU sends thefull-version uplink scheduling request to provide a comprehensive statusupdate to the Node-B with the minimum delay. In this scenario, thefull-version uplink scheduling request is transmitted as in-band controlsignaling.

A second scenario for when a full-version uplink scheduling request ispreferred is when M sub-frames have elapsed since the last time afull-version uplink scheduling request was transmitted although the WTRUhas a current scheduling grant, where the value of M is a designparameter. This ensures that the Node-B at least periodically obtainscomprehensive status information of the WTRU pertaining to uplinkscheduling.

According to the preferred embodiment of the present invention, theselection between a short-version uplink scheduling request and afull-version uplink scheduling request is made with a priority given tothe short-version, such that the full-version uplink scheduling requestsare transmitted substantially less frequently than short-version uplinkscheduling requests. This reduces the signaling overhead for uplinkscheduling requests without significant degradation of performance.

FIG. 1 is a flow diagram of an exemplary uplink scheduling requestprocess 100 including steps 105, 110, 115, 120, 125, 130, 135, 140, 145,150, 155 and 160 in accordance with the present invention. While aparticular sequence of method steps is shown for the process 100 as anexample, any alternative method step sequence may be performed. Forexample, steps 145, 150 and either one of steps 155 and 160 may beperformed before any one of steps 115, 125 and 135. In another example,step 135 may be performed before step 115 and/or step 125. In yetanother example, steps 115 and 120, or steps 125 and 130, or steps 135and 140, or steps 145, 150, 155 and 160, or steps 115, 120, 125, 130,135 and 140 may be removed from the process 100.

Referring to FIG. 1 , the WTRU has buffered (user) data to transmit to aNode-B (step 105), but needs to have a scheduling grant for uplink datatransmission. The WTRU then commences determining which uplinkscheduling request type the WTRU should transmit to the Node-B (step110). In this example, the first condition to examine is to determinewhether at least M sub-frames have elapsed since the last time afull-version uplink scheduling request was transmitted and the WTRU hasa scheduling grant (step 115), thus ensuring a minimum periodicfull-version scheduling request. If at least M sub-frames have elapsedsince the last time a full-version uplink scheduling request wastransmitted, then the WTRU transmits a full-version uplink schedulingrequest to the Node-B as L1/L2 control signaling or higher layersignaling over an uplink shared control channel (step 120). If it isdetermined at step 115 that less than M sub-frames have elapsed, theWTRU determines whether it is currently in an initial power up mode, orwhether the WTRU has been inactive for a predetermined period of time,or whether the WTRU is lacking a scheduling grant but still remains timesynchronized with the Node-B in the uplink, (i.e., scheduled uplinkshared channel for transmission) (step 125).

If the decision at step 125 is positive, then the WTRU transmits ashort-version uplink scheduling request to the Node-B as L1/L2 controlsignaling or higher layer signaling over a contention-based uplinkchannel (step 130). Alternatively, at step 130, the short-version uplinkscheduling request can be sent over a low-rate dedicated channel insteadof a contention-based uplink channel for the scenario where the WTRU islacking a scheduling grant but still remains time synchronized with theNode-B in the uplink.

If the decision at step 125 is negative, the WTRU determines if itsuplink scheduling request is to be attached to uplink ACK/NACK bitsand/or CQI bits that are transmitted in the current TTI/sub-frame (step135). If so, then the WTRU transmits a short-version uplink schedulingrequest to the Node-B as L1/L2 control signaling or higher layersignaling over an uplink shared control channel (step 140). If not, theWTRU determines whether the WTRU's current scheduling grant issufficient to complete the current transmission of buffered data by apredefined delay (step 145). If the WTRU's current scheduling grant issufficient, the procedure 100 ends, since there is no need foradditional scheduling grant and thus no need for an uplink schedulingrequest. If the WTRU's current scheduling grant is not sufficient, thenthe WTRU determines whether a sufficient scheduling grant will beprovided after the WTRU transmits K short-version uplink schedulingrequests to the Node-B (step 150). If K short-version schedulingrequests will result in a sufficient scheduling grant being allocatedfrom the Node-B, then the WTRU transmits a short-version uplinkscheduling request as in-band control signaling (step 155). Otherwise,the WTRU transmits a full-version uplink scheduling request as in-bandcontrol signaling (step 160).

FIG. 2 is a block diagram of a wireless communication system 200 inwhich the uplink scheduling request process of FIG. 1 is implemented.The wireless communication system 200 includes a Node-B 205 and a WTRU210.

The Node-B 205 includes a scheduling processor 215, a receiver 220, atransmitter 225 and at least one antenna 230. The scheduling processor215 is in communication with the receiver 220 and the transmitter 225.The antenna 230 is also in communication with the receiver 220 and thetransmitter 225. The transmitter 225 is configured to transmit, via theantenna 230, a scheduling grant to the WTRU 210 over a downlink (DL)channel 235.

The WTRU 210 includes a data buffer 240, a scheduling request processor245, a receiver 250, a transmitter 255 and at least one antenna 260. Thescheduling request processor 245 is in communication with the databuffer 240, the receiver 250 and the transmitter 255. The antenna 260 isalso in communication with the receiver 250 and the transmitter 255. Thetransmitter 255 is configured to transmit, via the antenna 260, anuplink scheduling request to the Node-B 205 over an uplink channel 265when the WTRU 210 has data in the buffer 240 to transmit in an uplinktransmission to the Node-B 205. The scheduling request processor 245 isconfigured to determine which type of uplink scheduling request shouldbe sent to the Node-B 205 over the uplink channel 265 when there isbuffered data in the data buffer 240 waiting to be transmitted in anuplink transmission to the Node-B 205 according to the conditional stepsof the procedure 100 described above.

The receiver 220 in the Node-B 205 is configured to receive, via theantenna 230, the uplink scheduling request transmitted by the WTRU 210over the uplink channel 265. The receiver 250 in the WTRU 210 isconfigured to receive, via the antenna 260, the scheduling granttransmitted by the Node-B 205 over the downlink channel 235.

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention. The methodflow chart provided in the present invention may be implemented in acomputer program, software, or firmware tangibly embodied in acomputer-readable storage medium for execution by a general purposecomputer or a processor. Examples of computer-readable storage mediumsinclude a read only memory (ROM), a random access memory (RAM), aregister, cache memory, semiconductor memory devices, magnetic mediasuch as internal hard disks and removable disks, magneto-optical media,and optical media such as CD-ROM disks, and digital versatile disks(DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit/receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) module.

The present invention may be implemented as a wireless transmit/receiveunit (WTRU), which includes but is not limited to a user equipment,mobile station, fixed or mobile subscriber unit, pager, or any othertype of device capable of operating in a wireless environment. Thepresent invention may also be implemented as a system of such a WTRUwith at least one base station or Node-B. The present inventionimplementation is applicable to the physical layer, and by way ofexample, may be in the form of a digital signal processor, software orhardware.

What is claimed is:
 1. A wireless transmit/receive unit (WTRU)comprising: a transmitter; and a processor; the processor is configuredto determine that acknowledgement/negative acknowledgement (ACK/NACK)information and channel quality information (CQI) are to be transmittedin an uplink control channel transmission; the processor is furtherconfigured to determine that a scheduling request is to be transmitted;the transmitter is configured to transmit a message in an uplink controlchannel transmission in response to the determination that ACK/NACKinformation and CQI are to be transmitted in a uplink control channeltransmission and in response to the determination that the schedulingrequest is to be transmitted, wherein, based on an amount of informationthat the message is capable of carrying, the transmitted messageincludes the scheduling request, the ACK/NACK information, and at leasta portion of the CQI; the processor is further configured to determinethat information indicating buffer status is to be transmitted; and thetransmitter is further configured to transmit the information indicatingthe buffer status as in-band information.
 2. The WTRU of claim 1,wherein the scheduling request is needed for transmission of buffereddata before a predetermined delay.
 3. The WTRU of claim 1, wherein themessage is transmitted in a sub-frame as L1 or L2 control information.4. The WTRU of claim 1 wherein the message is transmitted on a conditionthat a scheduling grant is insufficient for buffered data.
 5. The WTRUof claim 1, wherein status information or quality of service (QoS)requirements of the WTRU is transmitted along with the informationindicating the buffer status.
 6. The WTRU of claim 1, wherein the WTRUutilizes Long-Term Evolution (LTE) transmissions.
 7. The WTRU of claim1, wherein the scheduling request is prioritized over the informationindicating the buffer status.
 8. The WTRU of claim 1, wherein theprocessor is further configured to send, after a predetermined number ofsub-frames after transmission of the message, the information indicatingthe buffer status.
 9. A method performed by a wireless transmit/receiveunit (WTRU), the method comprising: determining thatacknowledgement/negative acknowledgement (ACK/NACK) information andchannel quality information (CQI) are to be transmitted in an uplinkcontrol channel transmission; determining that a scheduling request isto be transmitted; generating a message, the message comprising, basedon an amount of information that the message is capable of carrying, thescheduling request and at least a portion of the ACK/NACK informationand a portion of the CQI; transmitting a message in a uplink controlchannel transmission in response to the determination that ACK/NACKinformation and CQI are to be transmitted in a uplink control channeltransmission and in response to the determination that the schedulingrequest is to be transmitted, wherein based on an amount of informationthat the message is capable of carrying, the transmitted messageincludes the scheduling request, the ACK/NACK information, and at leasta portion of the CQI; determining that information indicating a bufferstatus is to be transmitted; and transmitting the information indicatingthe buffer status as in-band information.
 10. The method of claim 9,wherein the scheduling request is needed for transmission of buffereddata before a predetermined delay.
 11. The method of claim 9, whereinthe message is transmitted in a sub-frame as L1 or L2 controlinformation.
 12. The method of claim 9 wherein the message istransmitted on a condition that a scheduling grant is insufficient forbuffered data.
 13. The method of claim 9, wherein status information orquality of service (QoS) requirements of the WTRU are transmitted alongwith the information indicating the buffer status.
 14. The method ofclaim 9, wherein the WTRU utilizes Long-Term Evolution (LTE)transmissions.
 15. The method of claim 9, wherein the scheduling requestis prioritized over the information indicating the buffer status. 16.The method of claim 9 further comprising sending, after a predeterminednumber of sub-frames after transmission of the message, the informationindicating the buffer status.